Injection devices based on a separate delivery mechanism attachable to replaceable containers have found widespread use in many areas, such as medical delivery systems. This use is due to the flexibility and economy contained in the possibility of providing a reusable pump type device with more or less advanced machinery for preparing, dosing, controlling and monitoring the injection procedure. The replaceable container features can be limited to those necessary for safe confinement and simple expulsion of the pharmaceutical, features which furthermore may be adapted to each individual preparation type.
Delivery devices are known for use in more permanent set-ups, e.g. for hospital treatment situations. Such setups include few design restrictions. Also, the pump part can be highly sophisticated in view of motorized manipulation means, processor controlled operation and data collection as well as possible interfacing against other available instrumentation. Often, the design freedom is also utilized to make the pump part compatible with one or several existing or standardized cartridges, syringe or injection device types, thereby increasing the application range for the instrument and reducing adaptation costs for the cartridge part.
For ambulatory purposes, the design limitations are more severe, especially for self-contained devices without connectable support. Size and weight restrictions place limitations on the number and sophistication degree of functions possible to include. Automation as an alternative measure for increasing safety and avoiding misuse is similarly restricted by the added motorized means and operation repertoire by limited capacity of energy storage means. Although handy and portable injectors may be devised with the minimum of support features necessary to safely control all the above-said requirements and problems in the hands of a skilled operator, a general trend in long-term medication is to place the administration responsibility on the patient himself, also in the case of children or disabled persons, e.g. by use of pen-type injectors. A high degree of automation and control is then desirable to avoid mistakes, not only at the mere injection steps but also the critical initiation and preparation steps. Patients dependent on daily administrations also have a legitimate need for convenience and devices discrete enough to be carried around in daily life. The contradictory requirements on highly sophisticated and yet small and convenient devices need to be met by new technology.
Delivery devices both for permanent and ambulatory use need a reliable sensor system for container control and verification in broad sense. The mere range of container types attachable to the general purpose pumps for stationary use in itself creates a control problem. Also, for portable devices, the option of patient self-administration requires a fail-safe control and the widespread distribution of pumps and containers requires corresponding precautions against intended or unintended misuse or abuse. The reliance on automation for most functions in the devices assumes an input to the processor of, for example, the presence of a container, check of its condition, verification of its non-used status and information of container type, content, concentration, expiration date etc. It may also be desirable to input individual patient data and administration schemes. Even when the pump device is intended only for a single or a few container types or contents the pump should be inoperable except for with these containers, and also when intentional efforts are made to circumvent the safety system.
It is clear that the desirable controls may be of quite varying natures. Pure information may be transferred from a machine readable marking on the container to the device. Such information may be totally unrelated to the container, as in the case of patient data or a security code, or related thereto, as in the case of markings representing container preparation type and volume. Control of physical container characteristics, such as size and orientation, and functional properties, such as presence of preparation and plunger position, may require a non-standard design of the container with special features for sensing, a highly sophisticated all purpose monitoring system or multiple specialized sensors for each feature to be detected, all of which alternatives are incompatible with the abovesaid general demands placed on stationary or portable pump systems.
Common information carrying marking techniques are not suitable for the purposes outlined. U.S. Pat. No. 4,978,335 and International Patent Document WO 93/02720 suggest, among other things, the use of a bar code and a bar code reader for similar purposes. Bar codes do not carry much information on a given surface, require a reader of significant size which can not conveniently be housed in small devices, utilize complex radiation systems and the code, as such, is easily manipulated and, hence, not safe against forgery. Finally, the system is nor usable for sensing any container characteristic other than the specified coding. Similar disadvantages and restrictions are present with marking systems based on reading of alphanumeric characters, magnetic strips, etc.
Sensors for physical or functional container properties seem to be scarce in the prior art. Systems based on switches, as represented by U.S. Pat. No. 4,838,857 activated by a container when in proper position, give a highly inflexible sensing system unless a multitude of switches are arranged and a system susceptible to wear and contamination. Also, systems based on interlocking of mating structures, as exemplified by EP 549 694, are inflexible, unprecise and easily cheated and, to the extent special key features are provided on the cartridge part, not compatible with standard containers. Known principles seem to be highly specialized, easily manipulated and not adaptable for a complementary information reading.
Accordingly, there remains a need for a sensing system able to meet the various demands in medical delivery devices while being compatible with the typical restraints in these applications. Although the present invention has a more general utility, it will mainly be described against this background.